In a modern automotive vehicle, the engine is equipped with fuel injectors that spray precise quantities of fuel into the air stream flowing through a manifold to the combustion chambers. The fuel is distributed to the injectors through a fuel rail mounted on the engine. A computer controller calculates the precise quantity of fuel and the opening time required by the fuel injector to release the precise quantity. The opening time is dependent upon the pressure drop across the injector, which is in part determined by the fuel pressure within the fuel rail.
Mechanical returnless fuel systems are known for supplying fuel from a fuel tank to the fuel rail. A typical system comprises a fuel pump located within the fuel tank and connected to the fuel rail through a fuel line. Conventional mechanical returnless fuel systems seek to maintain a constant fuel pressure within the fuel rail and the fuel line. This is accomplished by a pressure regulator that is coupled to the fuel line and opens to discharge fuel to the fuel supply to thereby relieve excess pressure within the fuel line. Conventional fuel systems utilize a pressure regulator that comprises a diaphragm that opens to relieve the pressure. Such diaphragm-type regulators are effective to maintain substantially constant fuel pressure, but add significantly to the cost of the system.
The fuel system also typically includes one or more valves that include a spring-biased ball or the like and that are less expensive. Such ball valves open in response to fuel pressure, but tends to result in variations in opening pressure or pulsations in fuel line pressure. Thus, ball valves are suited for use as pressure relief valves or check valves where pressure variations do not adversely affect performance. For example, it is known that fuel line pressure increases during hot soak following hot engine operation and necessitates a pressure relief valve. However, ball valves are not suited for use to regulate pressure in a predictable manner that is required for precise engine control. As used herein, a distinction is made between a pressure relief valve that opens to relieve a significant overpressure greater than the desired operating pressure, and a pressure relief valve regulating fuel pressure at a desired operating valve. Fuel systems, referred to as electronic returnless fuel systems, have been developed that include spring-biased ball valves for pressure relief, but utilize pressure sensors and electronic controls to regulate fuel pump duty cycle to maintain a desired operating pressure.
Therefore, there exists a need for a pressure regulating valve for a automotive fuel system that opens to recycle excess fuel and produces a predetermined fuel pressure within the fuel line that is reliable for precise engine control, and that is less costly, particularly when compared to diaphragm-type pressure regulators.